JPH0558114A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To secure good straight running performance of a car and prevent generation of pattern noise and eccentric wear by dividing the tread into an inner and an outer zone by the bisector for the center and grounding end or that of the main grooves which are situated nearest the bisector, and arranging so that the inclination angle of slits over the two zones in the direction across the tire width lies within a specific range. CONSTITUTION:The surface of a tire tread is patterned with main grooves 3 stretching circumferentially and slits 5a, 5b in the crosswise direction and divided into an inner zone 6a and an outer zone 6b by a bisector for the center and grounding end or that of the main grooves 3a which are situated nearest the bisector. The inclination angles theta1, theta2 of the slits 5a, 5b in these zones 6a, 6b to the direction across the tire width shall lie in respective ranges such that theta1=32-40 deg., theta2=0-40 deg., theta1=-32 thru-40 deg., and theta2=0 thru -40 deg.. There plus sign (+) indicates an angle with the righthand elevated while the minus sign (-) an angle with the lefthand elevated. This permits lessening the residual CF pattern component which might affect the straight running performance, also lessening the pattern noise, and reduce the generation of eccentric wear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire mainly for passenger cars, and more particularly to a tire having a tread pattern including lateral grooves (slits) in the tire width direction.

[0002]

2. Description of the Related Art Vehicles such as passenger cars differ depending on the vehicle type, but drift to the tire due to the curvature and cord angle of the tire belt layer, the carcass structure, or the shape of the tire peripheral surface. The force may act to cause a phenomenon of skewing, a so-called one-sided flow phenomenon, which impairs the straightness of the vehicle.

It is known that such a one-way flow phenomenon of a vehicle has a very high correlation with the residual cornering force (hereinafter abbreviated as residual CF) of the tire of the front wheel. For example, for a vehicle, the residual CF of the tire,
The relationship with the amount of one-sided flow (the amount of lateral deviation when the vehicle is released by hand) is shown in the graph of FIG. When this is expressed by an equation, Y = a × residual CF + b.

In the above description, a and b are constants that change depending on the vehicle, but b is a value close to zero. Therefore, it is desirable that the residual CF be a value close to 0 because the condition of the tire having good straightness is that the one-sided flow amount (Y) is close to 0.

However, the road surface has an inclination (cant) due to the drainage of rainwater, and therefore, in order to drive the vehicle straight against the road surface cant, the residual CF is negative for the right-hand side traffic area. (-), Positive (+) for left-hand traffic areas is desirable.

The above residual CF can be adjusted by the cord angle and direction of the belt layer. Conventionally, the straightness is ensured by changing the cord direction of the belt layer depending on the destination. That is, in the case of a two-layer steel belt, which is a general belt structure for passenger car tires, a view of the tire from above is shown in FIG. 8A for the right-hand traffic area and in FIG. 8 (A) for the left-hand traffic area. The code direction was as shown in b). This is because when the second belt (B2) on the outer side (tread side) is moved to the upper left, the residual CF generates a negative force, and the second belt (B2)
This is because the residual CF generates a positive force when is set to the upper right.

However, depending on the shape of the tread pattern, the pattern component of residual CF may be generated due to the directionality of the pattern, and the amount of one-sided flow may still be large even with the above belt structure. That is, even in the tire for the right-hand side traffic area, the residual CF may be positive depending on the tread pattern.

Therefore, in order to secure the straightness of the vehicle by reducing the pattern component of the residual CF due to the directionality of the tread pattern, the inventor has
That is, various studies were conducted on the relationship between the inclination direction and angle of the lateral groove (slit) in the tire width direction and the residual CF.

For example, in a tire having a belt structure for the right-hand side traffic area shown in FIG. 8A, a tread having four main grooves (3) and lateral grooves (slits) (5) in the tire width direction shown in FIG. When the residual CF was measured by changing the slit angle for the tire having the pattern, the graph shown in FIG. 7 was obtained. (A) of the figure shows that the slit angle of the outer area (6b) from the main groove (3a) substantially in the center between the tread center (C) and the ground contact end (E) is 0 °, and the inner area (6
The angle (θ1) of the slit (5a) with respect to the tire width direction in (a) is changed.
It shows a case where the slit angle of a) is set to 0 ° and the angle (θ2) of the slit (5b) of the outer region (6b) is changed. The slit angle (+) indicates the upper right angle, and the (−) indicates the upper left angle.

In the belt structure for the left-hand side traffic area shown in FIG. 8 (b), the residual CF is considered to be a curve on the (+) side symmetrically with respect to FIG.

From the above measurement results, it has been found that the residual CF pattern component due to the directionality of the tread pattern suddenly occurs when the slit angle formed with respect to the straight line in the tire width direction exceeds 40 °.

According to the present invention, the slit angle is set on the basis of the above measurement result in order to reduce the pattern component of the residual CF.

Considering the relationship between the slit angle and the performance other than the straightness of the vehicle, the slit angle is preferably large with respect to (a) pattern noise, and the slit angle in the inner region is preferably large. On the other hand, it is preferable that the slit angle be small with respect to (b) uneven wear of the tire. In particular, the larger the slit angle in the outer region, the higher the occurrence rate of uneven wear.

Therefore, in order to make the straightness of the vehicle compatible with other performances such as prevention of pattern noise and uneven wear, the slit angle in the inner region is large, the slit angle in the outer region is small and the slit angle in the inner region is small. It is better to have the same inclination direction as the slit.

In view of this, the present invention specifies the range of the inclination angle of the slit of the tread pattern, particularly in the tire width direction, ensures the straightness of the vehicle, and is also effective in preventing pattern noise and uneven wear. We decided to provide pneumatic tires.

[0016]

That is, according to the present invention, two or more belt layers are provided on the outer side of a carcass ply, and a plurality of main grooves continuous in the tire circumferential direction are provided in a tread portion, and a tire is formed from the main grooves. In a pneumatic tire having a large number of slits extending in the width direction, a main groove existing on a line that bisects a center and a ground contact end in a tread portion or a main groove closest to the bisector is an inner region. And the outer area, and the inclination angle of the slit existing in the inner area and the slit existing in the outer area with respect to the tire width direction is set to the following angle range (a) or (b). ..

(A) Slit angle in the inner region 32 °
40 ° Outer Slit Angle 0 ° to 40 ° (b) Inner Slit Angle −32 ° to −40 ° Outer Slit Angle 0 ° to −40 ° (However, + is a rising angle, − is That is, when the angle of the slits in the inner region and the outer region with respect to the tire width direction, that is, the slit angle is larger than 40 °, a large pattern component is generated in the residual CF, which affects the one-sided flow amount. Not preferable. Further, if the slit angle in the inner region is smaller than 32 °, the pattern component of the residual CF is small, but the pattern noise is significantly generated, which is not preferable. Further, if the slit angle in the outer region exceeds the angle of 40 ° with respect to the tire width direction, the occurrence rate of uneven wear of the tread end portion becomes high, which is not preferable. It is particularly preferable to set the slit angle in the outer region smaller than the slit angle in the inner region from the viewpoint of preventing uneven wear.

The slit angle in the inner region and the slit angle in the outer region are the average inclination angles of the respective slits.

[0019]

According to the pneumatic tire of the present invention having the above-described structure, the inclination angle of the slit of the tread pattern, the slit angle of the inner area and the slit angle of the outer area are set to a specific angle range so that they are in the same inclination direction. Therefore, the pattern component of the residual CF that affects the straightness is small, and the amount of one-sided flow due to the directionality of the pattern does not increase.

Moreover, the slit angle in the inner area is the residual C
Since a large angle range is set within a range in which the pattern component of F becomes small, the pattern noise can be suppressed to a low level. The occurrence of wear can also be suppressed.

[0021]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 shows a sectional structure of a tire (T). In the drawing, (1) is a carcass ply, (B) is a space between the carcass ply and a tread portion (2) outside the (1). A belt (B1) consisting of two belt layers arranged and made of steel cords or cords of various industrial fibers
(B2) Two layers are laminated at a desired inclination angle and direction with respect to the tire circumferential direction. This belt layer may have three or more layers.

As shown in FIG. 2, the surface of the tread portion (2) has a plurality of (4 in the figure) main grooves (3) continuous in the tire circumferential direction, and the tire width from the main groove (3). Patterns are formed by the slits (5a) and (5b) extending in the direction (lateral direction).

Then, the main groove (3a) existing on the line (L) that bisects the center (C) and the grounding end (E) in the tread portion (2) or the closest to the line (L). It is divided into an inner region (6a) and an outer region (6b) with the main groove (3a) at the position as a boundary.

That is, as shown in FIGS. 2 and 3, when the main groove (3a) exists on the line (L) that bisects the center (C) of the tread portion (2) and the ground end (E). The inner area (6a) and the outer area (6) are separated by the main groove (3a).
b). When there is no main groove on the line (L), the inner area (6a) and the outer area (6b) are separated from the main groove (3a) closest to the line (L) as shown in FIG. Classify into and.

The tilt angle (θ1) between the slit (5a) in the inner area (6a) and the slit (5b) in the outer area (6b) with respect to the tire width direction.
(Θ2) is set to the angle range of (a) or (b) below based on the measurement result of FIG. (A) Slit angle in the inner area 32 ° to 40 ° Slit angle in the outer area 0 ° to 40 ° (b) Slit angle in the inner area −32 ° to −40 ° Slit angle in the outer area 0 ° to −40 ° In the figure, + indicates an upward rising angle, and − indicates an upward rising angle.

In the above, the slit angle (θ1) (θ
2) is the angle formed with respect to the straight line in the tire width direction of the slit center line when forming a straight line with a constant angle as shown in FIGS.

The slits are often partially bent as shown in FIGS. In this case, the slit angle is an angle formed by the straight line connecting the intersections of the circumferential straight line and the slit center line at the end of the main groove (3) with respect to the straight line in the tire width direction, and the inner region (6a) and the outer region. (6
Let b be the average angle for each slit (5a) (5b). However, the intersection of the outermost end of the slit (5b) in the outer region (6b) is the intersection of the slit center line and the ground contact end (E), and the straight line connecting this intersection and the intersection is the tire width direction. Make an angle.

Further, generally, for the purpose of reducing pattern noise, it is general that 3 to 5 kinds of slits having different slit angles are arranged at different pitches in the circumferential direction. In this case, the average of the plurality of slit angles is used.

(Example) The following tests were carried out on the tires for the right-hand side traffic area shown in FIG. 1 to examine one-way flow and pattern noise. The results are shown in Table 1 below. Further, for comparison, the same test was carried out for the slit angles outside the angle range of the present invention (Comparative Examples 1 and 2). One-sided flow and pattern noise are judged by the driver's sensory evaluation, and the standard is set to 6 1
It was displayed as an index in 0 steps.

Tire size: 185 / 60R14
82H ・ Tire air pressure: 1.8kgf / cm ²・ Lim: 14 × 5 1/2 -JJ ・ Test vehicle: Domestic vehicle ・ Road surface cant: 1% on the upper left (assumed for right-hand traffic area) ・ Vehicle speed: 100km / h

[0032]

[Table 1]

As is clear from the above test results, the one set in the angular range as in the present invention is standard in both the one-way sensory evaluation and the pattern noise sensory evaluation, and the straightness of the vehicle and the pattern noise prevention can be improved. It became compatible.

[0034]

As described above, according to the pneumatic tire of the present invention, the pattern component of the residual CF that affects the straightness is small, and the one-sided flow amount due to the directionality of the pattern does not increase. In addition, the pattern noise is small and the uneven wear rate can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a part of a tire showing an embodiment of the present invention.

FIG. 2 is a partial plan view schematically showing the above belt structure and pattern shape.

FIG. 3 is a partial plan view showing a tread pattern of the same.

FIG. 4 is a partial plan view illustrating another tread pattern.

FIG. 5 is an explanatory diagram of how to obtain a slit angle in the above.

FIG. 6 is a graph showing a correlation between residual cornering force and one-sided flow rate.

FIG. 7 is a graph showing changes in slit angle and residual CF.

FIG. 8 is a schematic plan view illustrating a belt structure.

[Explanation of symbols]

 (1) Carcass ply (2) Tread (3) Main groove (5a) Inner area slit (5b) Outer area slit (6a) Inner area (6b) Outer area (B) Belt layer (B1) First belt (B2) Second belt

Claims (2)

[Claims] 1. A carcass ply is provided with two or more belt layers on the outer side, and a tread portion has a plurality of main grooves continuous in the tire circumferential direction and a large number of slits extending from the main grooves in the tire width direction. In a pneumatic tire, a main groove existing on a line that bisects the center and the ground contact end in the tread portion or a main groove closest to the bisector is divided into an inner region and an outer region. A pneumatic tire characterized in that an inclination angle of a slit existing in an inner area and a slit existing in an outer area with respect to a tire width direction is set in the range of (a) or (b) below. (A) Slit angle in the inner area 32 ° to 40 ° Slit angle in the outer area 0 ° to 40 ° (b) Slit angle in the inner area −32 ° to −40 ° Slit angle in the outer area 0 ° to −40 ° ( However, + is a rising angle to the right, -is a rising angle to the left) 2. The pneumatic tire according to claim 1, wherein the slit angle in the inner region and the slit angle in the outer region are inclination angles of respective slit averages.